


In The Shallows

by t0bemadeofglass



Category: Marvel (Movies), The Avengers (Marvel Movies)
Genre: D/s undertones, Double Penetration, Established relationship Steve/Natasha, F/F, F/M, PWP, Plot What Plot/Porn Without Plot, Prompt Fill, Strap-On
Language: English
Status: Completed
Published: 2014-06-10
Updated: 2014-06-10
Packaged: 2018-02-04 03:11:01
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,780
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1763767
Author URL: https://archiveofourown.org/users/t0bemadeofglass/pseuds/t0bemadeofglass
Summary: <blockquote class="userstuff">
              <p>Natasha has a proposition for Steve that she's all too happy Sif is eager to join in.</p>
            </blockquote>





	In The Shallows

**Author's Note:**

> For the anon who wanted Sif, Nat, and Steve, with Nat and Steve in an established relationship, domming over Sif once she lost in a sparring match. Hope this works! Thanks so much for the prompt and I hope it turned out a-okay!

They’d talked about adding a third person into the mix for some time, at least for a month or so, but Nat wasn’t sure that anything would ever come of it if she was entirely honest.  Not that Steve usually had a problem--hell, since they’d gotten together she’d been impressed with how remarkably open he was to her less than conventional requests when it came to the bedroom.  Turned out spanking, collaring, and dirty talk was as up his alley as it was hers.  But a third partner?  

He seemed iffy at best.  The more she started listing off, both men and women just to be sure that she wasn’t pigeonholing him and honestly she wasn’t picky, the more often he’d give her a half hummed, non-committal noise that would force a snort from her and a sheepish grin from Steve.  Perhaps it wasn’t for everyone.  

She waited, growing silent on the subject, not wanting to push it too much too fast.  He did his best to make up for it, more than happy to indulge her every other fantasy, and for that she was more than thankful and appreciative, guilt rising when she considered how she’d pushed the subject before.  If it wasn’t for him then she had no right to force it on him, and instead decided to push it from her mind.  What sort of lover was she to involve him in something that wasn’t what he wanted?

Yet when she caught him slack-jawed and wide eyed as he watched Sif single handedly dismember one of the alien forces that’d thought Earth to be ripe for the picking after Loki had attacked, she couldn’t help but grin.  Perfect.  It made sense, and though her body went back to the task at hand, trying to catch up with Sif’s own impressive body count as Tony worked to shut down the alien craft allowing them to transport from one universe to the next, her mind nested the information for later use.  

Two days later, after everyone was on the mend, the injuries few and healing quickly enough that she felt comfortable taking a break from visiting the bedsides of her fellow fighters, she found the goddess speaking with him in the kitchen, her eyes bright as they compared blow by blow explanations of their own preferred method of fighting.  Nat hung back on the side of the door frame, leaning against it and grinning in spite of herself.  She couldn’t deny the warrioress was a sight for sore eyes: legs for days, long, black hair Natasha could imagine running her fingers through, and as quick a wit as Stark and herself, but there was more to her than that.  She and Steve shared kindred spirits, and if anything her fire and thirst to prove herself only reeled him in further, something that all three of them could understand.  

She left without saying a word, brain already forming a plan, and seeking out Thor.  She had a few questions about monogamy and Asgard, and just which buttons to press if she was looking for a certain, favorable reaction.  

 

“You’re sure about this?”  Steve asked for what must’ve been the dozenth time, and Natasha took his hand in hers and squeezed, nodding, lips twisted upwards in a pleased smile.  She was good, she was really damn good.  Twelve hours, two brief conversations with two different Asgardians, and one hella good pep talk later, and she was leading Steve down to the training rooms, Sif already waiting there for the pair of them.  The Asgardian had been questioned, propositioned, and now was patiently pacing back and forth in the soundproof room that Nat kept tugging Steve towards.  For once he hadn’t nixed Natasha’s suggestion, leading her to wonder how the hell it was she hadn’t thought of Sif before, and as she assured him with a kiss on the cheek that yes, she was damn certain about this, she felt her heart rate begin to quicken.  She’d done it, she’d actually figured it out.  

“Steve if you keep asking me if I’m sure I’m going to assume you don’t want this,” she told him as they rounded the final corner and he pulled her back, opening his mouth to say the same adorably thoughtful question as the last time.  “I want this, Sif does, and I know you do.  Right?”  

“I want you,” he assured her and squeezed her hand.  

“And?”

He flushed, and she grinned broadly.  Exactly, that was what she thought.  “Hey, this is going to turn out great, don’t worry about it,” she promised.  She’d already gone over the details to ensure it, but as doubt flashed across his face she paused at the door and held him back from entering.  

“Steve,” she said, voice quiet.  “Be honest with me now.  Are you really not alright with this?”  She asked, her head tipped up so that their eyes could meet.  He swallowed thickly, and let out a deep, heavy sigh, shaking his head.  

“I’m just nervous, Natasha.  We haven’t been together long, and I know you want this but--.”

“Hey, don’t worry about it.”  She promised, her face softening as her heart ached.  She hadn’t meant to push him, not like that.  Rising on her tip toes to kiss him she smiled as she pulled away.  “I just thought you liked her.  Of all the others, I figured if you’d ever wanted to do this it’d be with Sif and I.  All three of us.”  

He bit his lip, his attention turning to the side as he considered it.  

“But if you don’t want it then that’s fine.  Just as long as you communicate with me.”  

He paused and nodded, kissing her once more.  “I can do that.  Maybe . . . can we just give it a few days?  I can explain to Sif--.”  

Natasha shook her head, taking his shoulder in hand and standing on her toes to grin up at him.  “I’ve got it.  We’ll give it a week, how’s that?  Gives us more time to get it all figured out and if you’re still not ready then we’ll hit that when we get there.”  

He couldn’t have looked more relieved at that, and excused himself as Natasha moved to speak with Sif about the situation.  It gave them more time to plan it out, and the goddess was all too understanding of the situation, promising that whenever they were ready she would be the same.  Natasha kissed her quickly on the lips, smiling when she pulled back.  “You are the very best, Sif.”  

The smile shared between the two of them made Natasha’s stomach flutter a little.  One week.  One week of planning, and hopefully, if she played her cards right and didn’t push it, she’d get some results that’d please all of them.

 

The week past, Natasha did everything she could to ease him into the idea, and when the time finally came she was pleased to see he wasn’t shaking, wasn’t near as nervous as he had been the time before.  Her fingers were threaded with his as she led him towards the training rooms for the second time.  They’d gone over what would happen half a dozen times, Steve always initiating, Natasha more than happy to play along until he felt confident enough in the plans.  She liked him confident, and kissed his cheek before they walked in, watching as he slung the bag he’d brought down on the ground.  Whatever was in it was as much a secret to her as it was Sif, and it made her gut clench in anticipation.  

“Ready?”

“As I’ll ever be.”  

Sif was waiting, as last time, leaning up against one of the walls near the sparring portion of the gym.  As Steve took a moment to lock the door behind them and disable the cameras, Natasha walked up to Sif with a new sway in her hips, a smirk already crossing her lips.  

“Good to see you again, Sif.”

“My lady,” the goddess inclined her head half an inch or so.  Her pupils were already dilated, and her lips twisted in a wide grin.  “Pleasure to see you both.  I trust everything is going to plan?”  

“Yes.  You’re still game?”  

Sif’s head tipped to the side at the phrasing, but after gleaning the idea she nodded with a grin.  “Certainly.  I would not back down.”  

Perfect, then.  They went over the rules and scenario that Steve had helped Natasha to craft and Sif had agreed on.  They would spar, and the first to fall would be the one to sub, while the other two took their turns taking the reigns.  Sif and Natasha shared an easy grin with one another as Steve flushed a light pink, rubbing the back of his head, but when his head popped up to stare at them he was resolute as ever.  Good.  Natasha shared one last kiss with him before moving to the side and rolling her shoulders, cracking her neck as quick as she could manage.  Sif’s eyes were closed as she balanced herself on the tops of her toes, while Steve just watched the other two women, getting his head in the game.  Nat had seen him do it before, especially when they were contemplating a particularly difficult or out of the box scene.  

“Everyone is alright with red, yellow, and green?”  She double checked.  The others agreed, and as soon as Sif was finished there was a half second’s pause.  Steve bolted for Natasha at the same time Sif did, and though Natasha dropped with ease to the ground, rolling under one of Sif’s higher aimed kicks and thrusting her leg out to try and trip the woman up, the Asgardian jumped over the extended limb and lashed out once more.  She hadn’t, for whatever the reason, anticipated Steve coming behind her and landing a blow to her gut.  She’d had worse, Natasha could read it on her face though she doubled over and pretended it had fatally hurt her.  Steve fell for it, his face immediately going surprised as he rushed to her aid, not used to fighting against Sif rather than alongside, and the goddess took her chance, tackling him to the ground.  

As Steve’s back hit the ground Natasha took her opportunity to lunge forward and grab her arms, twisting them as hard behind the woman’s back as she could.  The sudden binding of her arms threw the goddess momentarily off balance, and Natasha used it to her advantage, dragging the woman backwards with her.  Even as she crashed down to the ground on her back, her legs slipping around Sif’s, she held as fast as she could, hoping Steve would be up to get it going from there.  Above her Sif writhed, trying to break free, and Nat winced as the woman threw her head back to try and connect with Natasha.  Steve, who was far taller and stronger than Natasha, stood and snagged Sif’s hands from Natasha’ his grip tight enough to bruise as he pinned them above Natasha and Sif’s heads, freeing up Nat’s hands.  One of them snaked around to her front, taking one of her breasts in hand through the fabric and massaging it as she widened Sif’s legs with her own.  Steve slotted himself in between them with ease, and Sif gave a soft, shuddering moan as she felt Steve pressing against her, likely hard.  Though the sparring had only lasted a few minutes at most it was enough to get him excited for what was to come.  Sif stiffened in Natasha’s hold as Nat’s other hand snaked downwards, towards Sif’s trousers.  

“What color are we at?”  She hissed in Sif’s ear.  

“Green is good, right?” Sif asked, voice a gasp as Steve thrust his hips hard against hers.  

“Yes.  It means keep going.”

“Very, very green.”  

Natasha grinned from beneath her and sucked on Sif’s throat as she rolled her hips upwards, squishing the goddess between herself and her boyfriend even further, the friction and slide of bodies on one another near more than Steve could handle.  He growled from above them, his eyes hooded as he looked down at Sif.  “You gonna behave now, or we gonna have to tie you up?”  He asked, his voice edged with lust.  

“Mm, tie me up Captain,” Sif said as she stared up at him.  “If you and your woman can hold me then you deserve me.  If not, well, that’s not my problem.”  

Natasha’s teeth were sharp as they bit into Sif’s neck, and the goddess groaned at the fusion of pain and pleasure, her body shuddering.  Her reaction seemed to be one that Steve had very much been looking forward as he tugged her up to her feet, gripping her arms much in a same way that Natasha had as the spy got swiftly to her feet.  

“Natasha, there’s rope in my bag,” he said, jerking his chin in the direction and Nat went without wasting a moment.  The rope felt heavier, thicker, than any other type she’d had experience with before, and she couldn’t help but suspect he’d gone to Thor or someone to get specific rope for such a situation.  What a dog.  She grinned as she walked over, and without skipping a beat Steve demonstrated his own skill with tying knots.  As he worked Natasha buried her hand in Sif’s thick black hair before kissing her hard, the clash of teeth and tongue making the goddess release an uncharacteristic whimper as Steve quickly divested her of her trousers, having already ripped open the training tank top she’d donned.  Good of her to at least pick something disposable.  As Steve eased her to the ground Natasha went with them, shimmying out of her own shorts and watching as Steve kept Sif on her knees.  One of his hands shot between her legs, rubbing her already wet cunt with a hand well trained in evoking as much pleasure, or pain, as one could stand.  Natasha pressed her thighs together as she watched them, eyes hooded, and as Steve pushed two fingers into Sif with a soft grunt at the heat of her body, he pressed the goddess down onto her front.  

Natasha didn’t miss a moment, scooting forward so that Sif’s mouth was poised right above her own slit, legs spread wide and one of them going as far as to hook over Sif’s shoulders.  

“Show me what centuries of practice looks like, Sif,” Natasha murmured.  “You were always telling me how good you are.  Show me.”  

From between Nat’s legs, Sif’s eyes flashed, and her tongue flashed out to lick Nat from the bottom to the top of her cunt, swirling Natasha’s clit hard enough to make the spy whine and her arms, which were currently holding her up, to weaken.  As she worked at making Natasha moan, Steve had deftly undone his fly and had a hand around his cock, palming it as he watched Natasha shiver and thrash with every stroke of Sif’s tongue.  One of his hands ran down the middle woman’s back, feeling the soft skin in comparison to the rope he’d tied her up with, watching as it reddened her skin the same way his hand did as it came down on her backside.  The first slap made Sif jump and work all the harder, thrusting her tongue into Natasha, assuming that the reason she was on the receiving end was that she needed to pick up the pace.  Nat wasn’t about to complain, torn between laying back and letting Sif work, letting herself go boneless in the process, and watching the woman eat her out.  Both were infinitely appealing, Nat unable to tear her eyes away from how Sif’s every motion seemed to lend itself to making Nat feel as good as possible, whether it was the forward rocking motion of her body that brought on the quick addition of teeth to her clit, making Natasha shout in surprise, or the way that Steve shifted Sif’s body slightly to the side, causing her to shove her tongue as far into Natasha as it could go.  

Either way she was close to her first orgasm as Steve, with one finger of his own on Sif’s clit, slid into her as easily as if she was made for him.  The goddess choked on a sob of pleasure, and her work between Natasha’s legs faltered.  The spy gave a groan of displeasure, digging her heel into Sif’s back to try and urge her on, as Steve pushed all the closer and bottomed out with a muffled growl.  

“So tight,” he couldn’t help but mutter, reaching over to grasp Sif’s hair in hand and press down, grinding her face against Natasha’s slit as he pulled out, then slammed back into her.  Both women shouted, the vibrations of Sif’s own muffled words making Nat shudder, her hips rolling into the sharp, quick thrusts of Sif’s tongue, mimicking the same movements Steve was making just behind her.  

It didn’t take Nat much longer than that and her back arched as she screamed and grasped at the mat beneath them, nails tearing at the plastic covering as her voice echoed around the room over the soft undercurrent of Steve praising Sif for her good work.  His grip on Sif’s hair tightened as he pulled her up and away from Natasha’s sex, turning Sif’s head to kiss her hard on the lips, forcing his tongue into his mouth as she relaxed in his broad arms and let him.  

He moaned when he pulled away.  “Natasha I near forgot how delicious you tasted,” he said, beckoning the spy over, who crawled on shaky legs and rose on her knees to press Sif between the both of them as she and Steve kissed.  Though Natasha would be considered one of Sif’s dom’s, she knew where her place was where Steve was concerned, and easily yielded to his invading kiss, shivering when one of his hands reached out to rub her shoulders, then palm her breasts through the shirt she still wore.  

“Go get your other toy from my bag,” he whispered, voice hoarse and lips swollen from kissing when they pulled away.  Gone was the shy, unsure Steve of the week before, of even a half hour before, and the authority in his voice made her shudder before she dug through the bag.  She grinned when her fingers clasped around the strap on, the harness familiar to her as her fingers nimbly wrapped it around her hips.  She took a small vial of lube out along with it, squirting some of it onto the black, silicone head of the dildo and spreading it over the smooth surface.  It bobbed as she walked back towards them, Steve’s hips snapping against Sif’s as the goddess took in the sight coming towards her.  Her eyes widened and her mouth gaped, even as Steve shoved his thumb inside it and kept her mouth open.  

“Make some noise for me, Sif,” Steve murmured in her ear, Natasha just within hearing range.  The goddess whined as she ran her tongue over the pad of Steve’s thumb, her breath hitching with every thrust of his hips into her.  Natasha had just knelt down in front of her as Steve pulled out.  

“You want the front or the back, babe?”  Steve murmured, grinning as his blue eyes met Natasha’s.  

“Front is fine with me.  Don’t stop, by all means.”  She said without hesitation, kissing her way down Sif’s throat, nipping at the skin and purpling it until she reached the goddess’s breasts, sucking and licking at the underside until Sif’s back arched.  Steve, meanwhile, worked a finger, then two, slowly into Sif’s ass, panting as he staved off his own orgasm though the noises coming from her mouth were far too intoxicating.  

“Still green, darling?”  Steve asked from behind, panting hard against the back of her neck.  

“Mfm, yeah,” Sif said with a quick nod from around his thumb, Steve having moved it out of the way so she could speak.  If anything he drove his third finger further into her, scissoring her open, as Nat pressed the tip of her own cock into Sif’s cunt, driving upwards into her with a grunt and a snap of her hips.  Steve joined her soon after, Sif whining as the pair of them pressed her between them.  

“God, you’re so good, Sif,” Natasha said, fingers running over Sif’s hip bones, covered in a thin layer of sweat, and squeezing hard enough to bruise.  “Such a good girl.”

Blissed out, Sif barely managed a thanks as Steve’s thrusts countered Natasha’s, the pair of them countering one another’s thrusts.  Steve felt himself growing closer to the edge, and reached around Sif to kiss Nat once more.  She felt his desperation, felt Sif’s own tightly coiled desire ready to spring at any moment, and shifted one hand between them to rub at the goddess’ clit furiously with her thumb.  

“I want you to come for me, Sif.  For us,” she said with a wide grin, sucking on the woman’s bottom lip before kissing her.  She could still taste the remnants of her own orgasm on the goddess’ tongue and it made her groan and press herself all the closer to Sif, abandoning her grip on Sif’s hips in order to take a good hand full of her backside.  “Mm, love you so much--you’re so good.  C’mon, Sif.  Come now.”  

The moan that was ripped out of the dark haired woman’s throat was guttural to an extreme, coming from the tips of her toes and strangling her as it worked its way out of her lips.  Steve’s own mimicked it in depth as his hips pistoned into Sif, chasing his own orgasm as she tightened around him, coaxing the orgasm from whether he was ready or not.  Whoops.  

 

They cleaned up quickly after that, Sif covered in bruises and grinning broadly as she kissed them both before leaving.  Nat’s own smile mirrored hers as she turned around to face Steve.  “So, not that bad, huh?”  

He snorted as he pulled his shirt back on, his smile wry.  “No.  Not bad, not at all.  You gonna rub it in my face if I tell you that you were right?”

“Maybe,” she said with a shrug of one of her shoulders, wrapping one arm around his shoulders and tugging him down for a kiss.  “Till you teach me a lesson at least.”  The smack on her backside elicited a quick shout, and a grin on her lips.  That was what she was talking about.  

 

 


End file.
